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Processing, Characterization and Erosion Wear Behaviour of Coir Fiber Reinforced Epoxy Composites

Geetanjali Das

Mechanical Engineering

National Institute of Technology Rourkela

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Processing, Characterization and Erosion Wear Behaviour of Coir Fiber Reinforced

Epoxy Composites

Dissertation submitted to the

National Institute of Technology Rourkela in partial fulfillment of the requirements

of the degree of Master of Technology

(By Research) in

Mechanical Engineering by

Geetanjali Das (Roll Number: 612ME306)

under the supervision of

Prof. Sandhyarani Biswas

January, 2016

Department of Mechanical Engineering

National Institute of Technology Rourkela

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Mechanical Engineering

National Institute of Technology Rourkela

Certificate of Examination

Roll Number: 612ME306 Name: Geetanjali Das

Title of Dissertation: Processing, Characterization and Erosion Wear Behaviour of Coir Fiber Reinforced Epoxy Composites

We the below signed, after checking the dissertation mentioned above and the official record book (s) of the student, hereby state our approval of the dissertation submitted in partial fulfillment of the requirements of the degree of Master of Technology (By Research) in Mechanical Engineering at National Institute of Technology Rourkela. We are satisfied with the volume, quality, correctness, and originality of the work.

Sandhyarani Biswas Principal Supervisor

R. Sarkar Member (MSC)

P. Choudhury Member (MSC)

S. Ghosh Member (MSC)

Meghanshu Vashista Examiner

K.P. Maity Chairman (MSC)

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Mechanical Engineering

National Institute of Technology Rourkela

Prof. Sandhyarani Biswas

Assistant Professor

Supervisor's Certificate

This is to certify that the work presented in this dissertation entitled ―Processing, Characterization and Erosion Wear Behaviour of Coir Fiber Reinforced Epoxy Composites‖

by ―Geetanjali Das‖, Roll Number 612ME306, is a record of original research carried out by him under my supervision and guidance in partial fulfillment of the requirements of the degree of Master of Technology (By Research) in Mechanical Engineering. Neither this dissertation nor any part of it has been submitted for any degree or diploma to any institute or university in India or abroad.

Sandhyarani Biswas

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Dedicated to

My Beloved Parents, Son and

Husband

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Declaration of Originality

I, Geetanjali Das, Roll Number 612ME306 hereby declare that this dissertation entitled

―Processing, Characterization and Erosion Wear Behaviour of Coir Fiber Reinforced Epoxy Composites‖ represents my original work carried out as a postgraduate student of NIT Rourkela and, to the best of my knowledge, it contains no material previously published or written by another person, nor any material presented for the award of any other degree or diploma of NIT Rourkela or any other institution. Any contribution made to this research by others, with whom I have worked at NIT Rourkela or elsewhere, is explicitly acknowledged in the dissertation. Works of other authors cited in this dissertation have been duly acknowledged under the section ''Bibliography''. I have also submitted my original research records to the scrutiny committee for evaluation of my dissertation.

I am fully aware that in case of any non-compliance detected in future, the Senate of NIT Rourkela may withdraw the degree awarded to me on the basis of the present dissertation.

Geetanjali Das NIT Rourkela Roll Number: 612ME306

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Acknowledgment

It gives me immense pleasure to express my deep sense of gratitude to my supervisor Prof.

Sandhyarani Biswas for her invaluable guidance, motivation, constant inspiration and above all for her ever co-operating attitude that enabled me in bringing up this thesis in the present form.

I am grateful to Prof. Sunil Kumar Sarangi, Director, National Institute of Technology, Rourkela who has been a constant source of inspiration for me. I am equally grateful to Prof.

Siba Sankar Mahapatra, Head of the Department of Mechanical Engineering for his help and cooperation. I also appreciate the encouragement from faculty members of the Mechanical Engineering Department of National Institute of Technology, Rourkela.

I would like to record my sincere thanks to Prof. K. P. Maity, Prof. R. Sarkar, Prof. P.

Choudhury and Prof. S. Ghosh, learned members of my MSE scrutiny committee for being helpful and generous during the entire course of this work.

I greatly appreciate and convey my heartfelt thanks to Siva Bhaskara Rao Devireddy, Priyadarshi Tapas Ranjan Swain and Prabina Kumar Patnaik scholars associated with our department and all my well-wishers for their support and co-operation that is difficult to express in words.

My very special thanks go to all my parents, son and husband for their understanding, support and encouragement that enabled me to complete this work. I am also thankful to all those who have directly or indirectly helped during my research period

Finally, but most importantly, I thank Almighty God, my Lord for giving me the will power and strength to make it this far when I didn‘t see a light.

Geetanjali Das

NIT Rourkela Roll Number: 612ME306

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Abstract

Now-a-days, natural fibers have been receiving considerable attention as the substitute for synthetic fiber reinforcement such as glass in plastics. Among various fibers, coir is most widely used natural fiber due to its advantages like easy availability, low cost, low density, low production cost and satisfactory mechanical properties. The objective of the present research work is to study the physical, mechanical, water absorption and erosion wear behaviour of coir fiber reinforced epoxy composites filled with Al2O3 filler. Twenty different samples without filler and twenty samples with constant filler content of 10 wt% were prepared by varying the length of the fiber (3 mm, 6 mm, 9 mm, 12 mm and 15 mm) and content of fiber (5 wt%, 10 wt%, 15 wt% and 20 wt%) using hand lay-up technique. The density, hardness, tensile strength, tensile modulus, flexural strength, impact energy and percent of water absorption of the composites were analyzed. The erosion wear of these composites have been evaluated at different impingement angles (30°, 45°, 60°, 75° and 90°) and at different impact velocities (48 m/s, 70 m/s, 82 m/s and 109 m/s). The effect of fiber length and content on the properties of composites is also analyzed. A comparison has been made between composites with and without Al2O3 filler. It has been observed that composites filled with Al2O3 filler shows better mechanical and wear properties as compared to composites without filler. A multi-criteria decision making approach called TOPSIS is also used to select the best material from a set of alternatives. The morphology of eroded surfaces is examined by using scanning electron microscopy (SEM) and possible wear mechanisms are discussed.

Keywords: Al2O3 Particulate; Coir Fiber; Polymer Composites; Fiber Length; Fiber Content; Erosion Wear; Mechanical Properties.

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Contents

Certificate of Examination iii

Supervisor’s Certificate iv

Dedication v

Declaration of Originality vi

Acknowledgment vii

Abstract viii

List of Figures xi

List of Tables xiii

1 Introduction 1

1.1 Background and Motivation ………. 1

1.2 Thesis Outline………... 6

2 Literature Review 7 2.1 On Natural Fiber and Natural Fiber Reinforced Composites……… 7

2.2 On Mechanical Properties of Natural Fiber Composites……….. 11

2.3 On Coir and Coir Fiber Reinforced Composites………... 13

2.4 Use of Fillers in Polymer Composites……….. 14

2.5 On Erosion of Polymer Composites………. 15

2.6 On TOPSIS……….. 17

2.7 The Knowledge Gap in Earlier Investigations……….. 18

2.8 Objectives of the Present Work………. 18

3 Materials and Methods 20

3.1 Materials……… 20

3.1.1 Matrix Material……….. 20

3.1.2 Fiber Material ………... 21

3.1.3 Particulate Filler Materials……… 22

3.2 Composite Fabrication……….. 22

3.3 Physical and Mechanical Tests………. 24

3.3.1 Density……….. 24

3.3.2 Micro-hardness……….. 25

3.3.3 Tensile Strength………. 25

3.3.4 Flexural Strength………... 26

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3.3.5 Impact Strength………. 27

3.4 Scanning Electron Microscopy………. 27

3.5 Water Absorption Test……….. 28

3.6 Erosion Test ………. 28

3.7 TOPSIS Method……… 31

4 Results and Discussion: Physical, Mechanical and Water absorption Behaviour of Composites 34 4.1 Physical and Mechanical Properties of Composites………. 34

4.1.1 Density and void content………... 34

4.1.2 Tensile properties……….. 37

4.1.3 Flexural strength……… 41

4.1.4 Hardness……… 43

4.1.5 Impact strength………. 44

4.2 Water Absorption Behaviour……… 46

4.3 Fractography………. 52

5 Results and Discussion: Erosion Wear Behaviour of Composites 54

5.1 Erosion Wear Behaviour of Composites……….. 54

5.1.1 Steady state erosion……….. 54

5.2 Surface Morphology………. 62

6 Ranking of the Materials 65

7 Conclusions 74 7.1 Recommendation for Potential Application……….. 75

7.2 Scope for Future Research……… 76

Bibliography 77

Dissemination 90

Vitae 91

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xi

List of Figures

2.1 Classification of natural fibers……… 8

2.2 Structure of natural fiber………. 10

3.1 Pictorial views for collection of coir fiber……….. 21

3.2 Al2O3 filler……….. 22

3.3 Coir fiber reinforced epoxy composites………. 24

3.4 Experimental set up for micro-hardness test…... 25

3.5 Universal testing machine (Instron 1195) and loading arrangement for tensile and flexural tests……… 26

3.6 Izod impact testing machine……….. 27

3.7 Scanning Electron Microscope (JEOL JSM-6480LV)……….. 28

3.8 Solid particle erosion test set up (1) sand hopper, (2) conveyor belt system for sand flow, (3) pressure transducer, (4) particle-air mixing chamber, (5) nozzle, (6) x–y and h axes assembly, (7) sample holder……… 30

3.9 Schematic diagram of an erosion test rig……… 31

4.1 Effect of fiber content and fiber length on density of composites……….. 35

4.2 Effect of fiber content and fiber length on void content of composites……….. 35

4.3 Effect of fiber content and fiber length on density of composites filled with Al2O3 filler………. 36

4.4 Effect of fiber content and fiber length on void content of composites filled with Al2O3 filler……….. 37

4.5 Effect of fiber content and fiber length on tensile strength of composites………. 39

4.6 4.7 Effect of fiber content and fiber length on tensile modulus of composites……… Stress/strain curve for coir fiber reinforced epoxy composites without filler….. 39

40 4.8 Effect of fiber content and fiber length on tensile strength of composites filled with Al2O3 filler……….. 40

4.9 Effect of fiber content and fiber length on tensile modulus of composites filled with Al2O3 filler……….. 41

4.10 Effect of fiber content and fiber length on flexural strength of composites…….. 42

4.11 Effect of fiber content and fiber length on flexural strength of composites filled with Al2O3 filler……….. 42

4.12 Effect of fiber content and fiber length on micro-hardness of composites……… 43

4.13 Effect of fiber content and fiber length on micro-hardness of composites filled with Al2O3 filler……….. 44

4.14 Effect of fiber content and fiber length on the impact strength of composites….. 45

4.15 Effect of fiber content and fiber length on impact strength of composites filled with Al2O3 filler……….. 45

4.16 Water absorption behaviour of coir fiber reinforced epoxy composites with 5 wt% fiber content……… 48

4.17 Water absorption behaviour of coir fiber reinforced epoxy composites with 10 wt% fiber content……… 48 4.18 Water absorption behaviour of coir fiber reinforced epoxy composites with 15 49

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wt% fiber content………

4.19 Water absorption behaviour of coir fiber reinforced epoxy composites with 20

wt% fiber content……… 49

4.20 Water absorption behaviour of Al2O3 filled coir fiber reinforced epoxy

composites with 5 wt% fiber content……….. 50 4.21 Water absorption behaviour of Al2O3 filled coir fiber reinforced epoxy

composites with 10 wt% fiber content……… 50 4.22 Water absorption behaviour of Al2O3 filled coir fiber reinforced epoxy

composites with 15 wt% fiber content……… 51 4.23 Water absorption behaviour of Al2O3 filled coir fiber reinforced epoxy

composites with 20 wt% fiber content……… 51 4.24 SEM micrographs of fractured surface of composites after tensile and flexural

tests………. 52

4.25 SEM micrographs of fractured surface of composites filled with Al2O3 filler

after tensile tests………. 53

5.1 Effect of impingement angle on erosion rate of composites without filler at impact velocity of 48 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%……… 55 5.2 Effect of impingement angle on erosion rate of composites with Al2O3 filler at

impact velocity of 48 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%……… 56 5.3 Effect of impingement angle on erosion rate of composites without filler at

impact velocity of 70 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%…… 57 5.4 Effect of impingement angle on erosion rate of composites with Al2O3 filler at

impact velocity of 70 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%……… 58 5.5 Effect of impingement angle on erosion rate of composites without filler at

impact velocity of 82 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%…….. 59 5.6 Effect of impingement angle on erosion rate of composites with Al2O3 filler at

impact velocity of 82 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%……… 60 5.7 Effect of impingement angle on erosion rate of composites without filler at

impact velocity of 109 m/s (a) at fiber content of 5 wt%, (b) at fiber content of

10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%……. 61 5.8 Effect of impingement angle on erosion rate of composites with Al2O3 filler

impact velocity of 109 m/s (a) at fiber content of 5 wt%, (b) at fiber content of 10 wt%, (c) at fiber content of 15 wt%, and (d) at fiber content of 20 wt%…… 62 5.9 SEM of un-eroded surfaces of unfilled and Al2O3 filled coir fiber reinforced

epoxy composites (48 m/s, 10 wt%, 30°)………. 63 5.10 SEM of surfaces of the unfilled coir fiber reinforced epoxy composite (10 wt%,

3 mm, 30°)………... 64

5.11 SEM of surfaces of the Al2O3 filled coir fiber reinforced epoxy composite (10

wt%, 3 mm, 30°)……… 64

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List of Tables

2.1 Properties of Natural Fibers………... 9

3.1 Designation and detailed composition of the composites……….. 23

3.2 Experimental parameters for steady state erosion test………... 29

6.1 Decision matrix……….. 67

6.2 Normalized decision matrix………... 68

6.3 Weighted normalized decision matrix……… 69

6.4 Positive and negative ideal solution matrix……… 70

6.5 Separation Measure……… 71

6.6 Relative closeness value and ranking………. 72

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Chapter 1 Introduction

1.1 Background and Motivation

Engineering materials constitute the foundation of technology, whether the technology is applied to structural, thermal, electronic, electrochemical, biomedical, environmental or other applications. The history of human civilization is evolved from the Stone Age to the Bronze Age, the Iron Age, the Steel Age and to the Space Age [1]. Each age is marked by the advent of certain materials. The Iron Age brought tools and utensils, the Steel Age brought rails and industrial revolution, and the Space Age brought the even more advanced materials i.e.

composite materials. The development of composite materials and their related design and manufacturing technologies is one of the most important advances in the history of materials.

Basically, composites are materials consisting of two or more chemically distinct constituents, on a macro-scale, having a distinct interface separating them. One or more discontinuous phases are, therefore, embedded in a continuous phase to form a composite [2].

The properties of composite materials are superior in many respects, to those of the individual constituents. The discontinuous phase is usually harder and stronger than the continuous phase and is called the reinforcement, whereas, the continuous phase is termed as the matrix.

The primary functions of the matrix are to transfer stresses between the reinforcing fibers/particles and to protect them from mechanical and/or environmental damage whereas the presence of fibers/particles in a composite improves its mechanical properties such as strength, stiffness etc. The objective is to take advantage of the superior properties of both materials without compromising on the weakness of either. The composite materials have advantages over other conventional materials due to their higher specific properties such as tensile, flexural and impact strengths, stiffness and fatigue properties, which enable the structural design to be more versatile. Due to their many advantages they are widely used in aerospace industry, mechanical engineering applications (internal combustion engines, thermal control, machine components), electronic packaging, automobile, and aircraft structures and mechanical components (brakes, drive shafts, tanks, flywheels, and pressure vessels), process industries equipment requiring resistance to high-temperature corrosion, dimensionally stable components, oxidation, and wear, offshore and onshore oil exploration and production, marine structures, sports, leisure equipment and biomedical devices [3, 4].

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Generally, composite materials can be classified according to different criteria.

According to the type of matrix materials, composite materials are classified into three categories, such as metal matrix composites (MMCs), ceramic matrix composites (CMCs) and polymer matrix composites (PMCs). Each type of composites is suitable for different applications. Among various types of composites, PMC is the most commonly used composites, due to its advantages such as simple manufacturing principle, low cost and high strength. When the matrix material is polymer, the composite is called polymer matrix composites. The properties of PMCs are mainly determined by three constitutive elements such as the types of reinforcements (particles/fibers), the type of polymer, and the interface between them. Polymers are divided into two categories such as thermoplastics and thermosets. Thermoplastic are in general, ductile and tougher than thermoset materials and are used for a variety of nonstructural applications without fillers and reinforcements. They are reversible and can be reshaped by application of heat and pressure. Thermoplastic molecules do not cross-link and therefore they are flexible and reformable [5]. Properties of thermoplastic polymer include high strength and toughness, chemical resistance, good durability, self-lubrication, transparency and water proofing. However, thermoplastics show poor creep resistance, especially at elevated temperatures, as compared to thermosets. Their lower stiffness and strength values require the use of fillers and reinforcements for structural applications. Some of the thermoplastic polymer materials are nylon, acrylonitrile butadiene styrene, polycarbonates, polyethylene, polyetheretherketone, acetal, polyvinyl chloride etc.

Thermoplastic polymer are used to manufacture dashboard, toys, electrical products, bearings, gears, ropes, glass frames, hoses, sheet etc. Thermoset are materials that undergo a curing process through part fabrication and once cured cannot be re-melted or reformed. Thermoset materials are brittle in nature and offer greater dimensional stability, better rigidity, and higher chemical, electrical, and solvent resistance. The most common resin materials used in thermoset composites are epoxy, polyester, phenolics, vinyl ester, and polyimides.

Applications in which these are used are electrical equipment, motor brush holders, printed circuit boards, circuit breakers, encapsulation material, kitchen utensils, handles, knobs, spectacle lenses etc. Among them epoxy is the most widely used matrix due to its advantages like good adhesion to other materials, good mechanical properties, good electrical insulating properties, good chemical and environmental resistance etc.

According to the reinforcement, the polymer composites are classified into two categories such as particulate reinforced polymer composites and fiber reinforced polymer (FRP) composites. The particle reinforced composites mainly consisting of reinforcing material that is in the form particle. The shape of particles may be cubic, spherical, a platelet,

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tetragonal, regular and irregular geometry. The arrangement of the particles in the composites either randomly or preferred orientation. Usually the particles are used in reduce friction, improve machinability, electrical and thermal conductivities, improve performance at elevated temperatures, increase wear and abrasion resistance, reduce shrinkage and increase surface hardness of the materials. Recently, FRP composites have been widely used in various applications such as aerospace, automotive, marine etc. due to their advantages such as high specific stiffness and strength [6]. These materials also provide high durability, light weight and design flexibility, which make them attractive materials in these applications. FRP composites consisting of reinforcing fibers embedded in a rigid polymer matrix. Properties of FRP composites are determined by many factors such as properties of the fibers, fiber length, concentration of the fibers, orientation of the fibers, fiber-matrix interface strength, properties of the matrix etc. Therefore, in order to obtain the favoured material properties for a particular application, it is important to know how the material performance changes with these factors.

With the growing global energy crisis and ecological risks, natural fiber reinforced polymer composites have attracted more research interests due to their potential of serving as alternative for synthetic fiber reinforced composites. Compared to synthetic fiber based composites, the natural fiber composites are having the advantages such as low cost, easy availability, renewability, light weight and high specific strength, and stiffness [7]. A great deal of work has been done on the polymer composites reinforced with different types of natural fibers such as jute, banana, coir, wood fiber palm, flax and kenaf etc. [8]. Among them, coir fibers are extensively used now-a-days in many industrial applications. Coir is a natural fiber extracted from the husk of coconut fruit. It is a fiber which is highly available in India the second highest in the world after Philippines [9]. Coir fiber has many advantages like low cost, low density, versatile, high stiffness, renewability, waterproof, biodegradability and high degree of flexibility during processing [10]. Compare to other natural fibers, the coir fiber has remarkable interest in many industries due to its high hardness and hard- wearing quality, not toxic, good acoustic resistance, resistant to microbial and fungi degradation, and not easily combustible. The coir fibers are also more resistant to moisture than other natural fibers and withstand heat and salt water [11]. Coir consists of cellulosic fibers with hemi-cellulose and lignin as the bonding materials for the fibers. The fiber becomes stiffer, tougher and more long-lasting compared to other natural fibers because the lignin content in coir fiber is quite high. Coir fiber is widely used for preparing mats, ropes, mattresses, yarns, sacking, brushes, caulking boats, floor tiles and insulation panels etc. The coir fiber nets are used to prevent soil destruction during heavy rains and cyclones. It is reported that in the world about 55 billion of coconuts are produced yearly and only 15% of

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the coir fibers are actually recovered for use, leaving most coir abandoned. Coir based composites enjoying broader applications in automobiles and railway coaches & buses for public transport system. Coconut coir is a waste of natural resources and a cause of environment pollution. Hence, research and development efforts have been going on to find out the new areas for coir, along with utilization of coir as reinforcement in polymer composites. As reinforcement in polymer composites, coir fibers have demonstrated a great deal of potential. However, tribo-characterization of these coir composites is still in the formative stages [12]. In view of this, the present research work is undertaken to study the reinforcement potential of coir fibers in polymer composites.

Major constituents in FRP composites are the reinforcing fibers and a matrix. In addition, particulate fillers can also be used mainly to reduce the cost and improve the dimensional stability. The incorporation of these filler into polymer has been proved to be an alternative for the enhancement of the performance of the resultant composites and so has lately been a subject of considerable interest. So, even if a judicious selection of reinforcement and the matrix phase can lead to a composite with a combination of strength and modulus comparable to or even better than those of conventional metallic materials [13], the properties can further be modified by adding a solid filler phase to the matrix during the composite preparation. Such multi-component composites consisting of a matrix phase reinforced with a fiber and filler are termed as hybrid composites. The term ‗filler‘ is very broad and encompasses a very wide range of materials. Aluminium oxide (Al2O3) is a ceramic material that has the potential to be used as filler in various polymer matrices.

Generally, Al2O3 referred to as ‗alumina‘ which belongs to engineering ceramics family is the most cost effective and extensively used material. Al2O3 is hard, wear-resistant, has accomplished dielectric properties, resistance to strong acid and alkali attack at elevated temperatures, high strength and stiffness. With a superb combination of properties and a sensible value, it is no wonder that fine grain technical grade Al2O3 has a very wide range of applications.

Polymers and polymer composites are being used increasingly often as engineering materials for technical applications in which tribological properties are of considerable importance. The word tribology was first reported in a landmark report by Jost in 1966. The word is derived from the Greek word tribos meaning rubbing [14]. Since its definition, tribology has been widely recognized as a general concept embracing all aspects of the transmission and dissipation of energy and materials in mechanical equipment including the various aspects of friction, wear, lubrication and related fields of science and technology [15]. The enormous cost of tribological deficiencies to any national economy is mostly

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caused by the large amount of energy and material losses occurring simultaneously on virtually every mechanical device in operation. Wear is the surface damage or removal of material from one or both of two solid surfaces in a sliding, rolling, or impact motion relative to one another. Wear is not catastrophic but, in most cases, it certainly reduces operating efficiency. It results in dimensional changes of the components or damage to the surface.

This causes an associated problem of vibrations and/or misalignments. The propagation of cracks formed at or near the stressed surface may in extreme cases lead to fracture of the component. Components lose their applicability as a result of change in dimensions due to surface damage or wear. In engineering material science, wear are classified into five distinct types such as adhesive, abrasive, erosive, corrosive and surface fatigue. Solid particle erosion, a typical erosive wear mode, is the loss of material that results from repeated impact of small, solid particles. Polymer composites are finding applications that subjected to solid particle erosion. Examples of such applications are in petroleum refining pipe line carrying sand slurries, high speed vehicles and aircraft operating in desert environments, pump impeller blades, aircraft engine blades, water turbines, helicopter rotor blades etc. [16-18].

Hence, erosion resistance of polymer composites has become an important material property, particularly in selection of alternative materials and therefore the study of solid particle erosion characteristics of the polymeric composites has become highly relevant. Also a full understanding of the effects of all system variables on the wear behaviour is essential in order to undertake appropriate steps in the choice of materials and in the design of machine or structural component to reduce/control wear.

Material selection is one of the most challenging issues for designing and developing any structural component. The success of any component depends on the better performance and low cost of material used. Thus, it becomes a real challenge for the designers to optimally select material from the vast range of available materials that satisfy the complex design problems. Now-a-days, multi-criteria decision making (MCDM) approach is used as an effective tool for material selection of complex design problems [19]. The MCDM process involves creating alternatives, forming the required criteria and assessing the alternative materials using a set of criteria weights. The outcome of these steps is a ranked list of alternative solutions [20]. Various MCDM techniques like simple additive weighted (SAW) method, weighted product method (WPM), technique for order preference by similarity to ideal solution (TOPSIS), Vlse Kriterijumska Optimizacija Kompromisno Resenje (VIKOR) method, analytical hierarchy process (AHP), graph theory and matrix representation approach (GTMA), etc are used depending upon the complexity of the situation in engineering decision making problems [21-23]. Among various MCDM approaches, TOPSIS

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method offers a number of benefits [24]. The TOPSIS is one of the well-known MCDM method and was developed by Hwang & Yoon in the year 1981. The principle behind the TOPSIS is simple. Generally, ideal and negative-ideal solutions are formed. The ideal solution is formed as a composite of the best performance value exhibited by any alternative for each attribute and the negative-ideal solution is the composite of the worst performance values. The chosen alternative should be as close to the ideal solution as possible and as far from the negative-ideal solution as possible [25]. TOPSIS has been applied to a number of applications; however use of this technique for selection of materials is limited in the literature. Therefore, an attempt has been made to obtain the best alternative from the set of composite materials under the present study using TOPSIS.

To this end, the present research work is undertaken to study the physical, mechanical, water absorption and erosion wear behaviour of coir fiber reinforced polymer composites with Al2O3 filler. Attempts have been made to explore the potential use of coir fiber as reinforcement in polymer composites. The specific objectives of this work are clearly outlined in the next chapter.

1.2 Thesis Outline

The remainder of this thesis is organized as follows:

Chapter 2. Includes a literature review to provide a basic knowledge of the main subjects presented in this thesis. It presents the research works carried out by various investigators specifically on erosion wear behaviour of polymer composites.

Chapter 3. Provides detail information of the raw materials used, fabrication technique, test procedures, and characterization of the composites under study and also a description of TOPSIS method.

Chapter 4. Presents the test results of physical, mechanical and water absorption behaviour of composites.

Chapter 5. Presents the test results of erosion wear behaviour of the composites under study.

Chapter 6. Presents the ranking of composites using TOPSIS method.

Chapter 7. Provides summary of the findings of this research work, outlines specific conclusions drawn from the experimental investigation and suggests ideas and directions for future research.

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Chapter 2

Literature Review

The purpose of this literature review is to provide background information on the issues to be considered in this thesis and to emphasize the relevance of the present study. This treatise embraces various aspects of polymer composites with a special reference to their erosion wear characteristics. This chapter includes reviews of available research reports:

 On natural fiber and natural reinforced composites

 On mechanical properties of natural fiber composites

 On coir and coir fiber reinforced composites

 On use of fillers in polymer composites

 On erosion of polymer composites

 On TOPSIS

At the end of the chapter a summary of the literature survey and the knowledge gap in the earlier investigations are presented. Subsequently the objectives of the present research work are also outlined.

2.1 On Natural Fiber and Natural Fiber Reinforced Composites

Fibers in polymer composites can be either synthetic/man-made fibers or natural fibers. Some commonly used synthetic fibers for composites are glass, aramid and carbon etc. If the fibers are derived from natural resources like plants or some other living species, they are called natural fibers. It is also known that natural fibers are non-uniform with irregular cross sections, which make their structures quite unique and much different from man-made fibers.

Advantages of natural fibers over synthetic fibers include low density, high availability, low cost, recyclability and biodegradability [26]. The natural fiber based composites are classified into different categories according to their source of origin such as vegetable or plant fibers, animal or protein fibers and mineral fibers. Figure 2.1 shows the classification of the natural fibers [27]. The properties of some of these fibers are presented in Table 2.1 [28]. From the table it can be seen that the tensile strength of glass fiber is substantially higher than that of natural fibers even though the modulus is of the same order. However, when the specific modulus of natural fibers (modulus/specific gravity) is considered, the natural fibers show values that are comparable to or better than those of glass fibers. These higher specific

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Figure 2.1: Classification of natural fibers [27]

Bamboo Bagasse Rape

Rye Wheat

Oat Rice Barley Totora

Reed Corn Flax

Hemp Jute Kenaf Ramie

Uren Roselle

Isora Toina Nettle

Bast Leaf

Pineappl e Banana

Sisal Opuntia

Abacca Agaves Curaua Cabuye Palm

Seed

Cotton Poplar

Kapok Calotropis

Fruit

Coir Luffa

Grasses Wood

HardWood wood Softwood Mineral

Asbestos Wollastonite Plant or vegetable

Animal Wool

Silk Hair Chitin

Natural fiber

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properties are the major advantages of using natural fiber composites for applications where in the desired properties also include weight reduction.

Table 2.1: Properties of Natural Fibers [28]

Fiber Tensile strength (MPa)

Young‘s modulus (GPa)

Elongation at break (%)

Density (g/cm3)

Abaca 400 12 3-10 1.5

Alfa 350 22 5.8 0.89

Bagasse 290 17 - 1.25

Bamboo 140-230 11-17 - 0.6-1.1

Banana 500 12 5.9 1.35

Coir 175 4-6 30 1.2

Cotton 287-597 5.5-12.6 7-8 1.5-1.6

Curaua 500-1,150 11.8 3.7-4.3 1.4

Date palm 97-196 2.5-5.4 2-4.5 1-1.2

Flax 345-1,035 27.6 2.7-3.2 1.5

Hemp 690 70 1.6 1.48

Henequen 500 ± 70 13.2 ± 3.1 4.8 ± 1.1 1.2

Isora 500-600 - 5-6 1.2-1.3

Jute 393-773 26.5 1.5-1.8 1.3

Kenaf 930 53 1.6 -

Nettle 650 38 1.7 -

Oil palm 248 3.2 25 0.7-1.55

Piassava 134-143 1.07-4.59 21.9-7.8 1.4

Pineapple 400-627 1.44 14.5 0.8-1.6

Ramie 560 24.5 2.5 1.5

Sisal 511-635 9.4-22 2.0-2.5 1.5

E-Glass 3400 72 - 2.5

The natural fibers structure is very interesting because it consists of multi-layered structures as shown in Figure 2.2 [29]. The primary layer which forms cell growth and it surrounds the secondary layers. The position of middle layer is thick among secondary walls and that determines mechanical property of fiber. The main content of natural fiber is cellulose micro fibrils which are bonded by amorphous materials called hemicellulose. The angle between

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micro fibrils orientation in the structure and the axis of main fiber body is called microfibrillar angle. The microfibrillar angle is different for different natural fibers and that determines the mechanical strength of fibers. The main thing is that the natural fibers itself act as a composite material where amorphous materials like pectin, hemicellulose and wax acts as a matrix which bonds the microfibrillar cellulose. Generally, the hemicellulose molecules are creating hydrogen bond to microfibrillar cellulose and act as a binding material. Lignin acts as a coupling agent which helps to increase the stiffness of the cellulose/hemicellulose composite. The physical and mechanical properties of natural fibers are greatly influenced by their chemical compositions. The chemical composition of natural fibers may differ with the growing condition and test methods even for the same kind of fiber. Mechanical properties of natural fibers are much lower when compared to those of the most widely used competing reinforcing glass fibers [30]. However, because of their low density, the specific properties (property-to-density ratio), strength, and stiffness of plant fibers are comparable to the values of glass fibers [31]. Knowledge of different types of natural fibers, their structure, properties, and chemical composition is necessary for development of natural fiber reinforced polymer composites for use in a specific application.

Figure 2.2: Structure of natural fiber [29]

In recent years, natural fiber reinforced polymer composites have attracted increasing research interests owing to their potential as an alternative for composites reinforced with synthetic fibers like glass or carbon. A number of investigations have been made on the use of various natural fibers such as kenaf, hemp, flax, bamboo and jute as reinforcement for polymer composites. Saheb and Jog [4] have also presented a very elaborate and extensive review on natural fiber reinforced composites with special reference to the type of fibers,

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matrix polymers, treatment of fibers and fiber-matrix interface. Kozlowskiy and Wladyka- Przybyl [27] done a review on the use of natural fibers for polymer composites and study their fire performance. Li et al. [32], done a review on the use of different chemical modifications on natural fibers for use in natural fiber reinforced polymer composites. John and Anandjiwala [28] have done a critical review of the literature on the various aspects of natural fibers and natural fiber reinforced composites with a particular reference to chemical modifications. Taj et al. [33] examined the different types of fibers available and the current status of research on the use of these fibers for polymer composites. They also reported that the use of natural fibers within composite applications is being pursued extensively throughout the world. The diverse range of products now being produced, utilizing natural fibers and bio-based resins derived from soybeans, is giving life to a new generation of bio- based composites for a number of applications. These include not only automotive vehicles but also hurricane-resistant housing and structures. The construction sector and the leisure industry are some of the other areas where these novel materials are finding a market. Natural fiber reinforced composites can also be applied in the automobile and packaging industries to cut down on material cost.

2.2 On Mechanical Properties of Natural Fiber Composites

Generally, the mechanical properties of natural fiber composites are strongly influenced by many factors such as volume fraction of the fibers, fiber-matrix adhesion, fiber aspect ratio, fiber orientation, stress transfer at the interface etc. [34]. Therefore, both the matrix and fiber properties are important in improving mechanical properties of the composites. A great deal of work has already been done on the effect of various factors on mechanical behaviour of natural fiber reinforced polymer composites. Luo and Netravali [35] studied the tensile and flexural properties of green composites with different pineapple fiber content and compared them with the virgin resin. Srivastav et al. [36] have studied the effect of different loading rate on mechanical behaviour of jute/glass reinforced epoxy hybrid composites. Hu et al. [37]

studied the moisture absorption, tensile strength behaviour of short jute fiber/polylactide composite in hygrothermal environment. It was reported that for uncoated sample, the moisture absorption process includes three distinct stages such as quick moisture absorption stage, a slow steady increasing of moisture uptake stage and a very rapid moisture absorption stage. The whole moisture absorption process until the complete relaxation of the samples does not show moisture saturation. Schneider and Karmaker [38] developed composites using jute and kenaf fiber in polypropylene resin and reported that jute fiber provides better mechanical properties than kenaf fiber. Gowda et al. [39] evaluated the mechanical properties

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of jute fabric-reinforced polyester composites and found that they have better strengths than those of wood based composites. Basiji et al. [40] studied the effect of fiber length and fiber loading on the mechanical properties of wood-plastic (polypropylene) composites. Cazaurang et al. [41] carried out a systematic study on the properties of henequen fiber and pointed out that these fibers have mechanical properties suitable for reinforcement in thermoplastic resins. Dynamic mechanical analysis of natural fibers like sisal, pineapple leaf fiber, oil palm empty fruit bunch fiber etc. in various matrices has been made by Joseph et al. [42] and George et al. [43]. Harish et al. [44] studied the mechanical behaviour such as tensile strength, flexural strength and impact strength of coir/epoxy composites. Sapuan et al. [45]

carried out tensile and flexural tests on natural fiber reinforced musaceae/epoxy composites.

Similarly, an investigation on pulp fiber reinforced thermoplastic composite exhibited that while the stiffness is increased by a factor of 5.2, the strength of the composite is increased by a factor of 2.3 relative to the virgin polymer [46]. Shibata et al. [47] have investigated the effect of the volume fraction and length of natural fibers like kenaf and bagasse on flexural properties of some biodegradable composites. Luo and Netravali [35] studied the mechanical and thermal properties of environment-friendly "green" composites made from pineapple leaf fibers and poly (hydroxybutyrate-covalerate) resin. Tensile and flexural properties of the

"green" composites with different fiber contents were measured. Pavithran et al. [48]

determined the fracture energies for sisal, pineapple, banana and coconut fiber reinforced polyester composites using Charpy impact tests. They found that, except for the coconut fiber, increasing fiber toughness was accompanied by increasing fracture energy of the composites. Bos et al. [49] studied the mechanical properties of flax/polypropylene compounds, manufactured both with a batch kneading and an extrusion process. The structural characteristics and mechanical properties of coir fiber/polyester composites were evaluated and the effect of the molding pressure on the flexural strength of the composites was studied [50]. In another study, Okubo et al. [51] reported that the tensile strength and modulus of polypropylene based composites using steam-exploded bamboo fibers are higher than the composites using mechanically extracted fibers by about 15% and 30% respectively.

Chen et al. [52] tested the mechanical properties of bamboo fiber reinforced polypropylene and compared them with those of commercial wood pulp. Shin et al. [53-55] investigated the mechanical properties and fracture mechanisms of bamboo-epoxy composites under different loading conditions. They also compared the mechanical properties of various types of composites at different combination of fibers and resins. Chawla and Bastos [56] studied the effect of fiber volume fraction on Young‘s modulus, maximum tensile strength and impact strength of untreated jute fibers in unsaturated polyester resin, made by a leaky mould

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technique. Tobias [57] examined the influence of fiber content and fiber length in banana fiber reinforced epoxy composites and noticed that the impact strength increased with higher fiber content and lower fiber length. Hepworth et al. [58] investigated the mechanical behaviour of unidirectional hemp fiber reinforced epoxy composites. Alamri et al. [59]

studied the mechanical and water absorption behaviour of recycled cellulose fiber reinforced epoxy composites. It was observed that exposure to moisture for two weeks caused a reduction in flexural strength, flexural modulus and fracture toughness due to the degradation of bonding at the fiber-matrix interfaces. However, impact strength was found to increase slightly after water absorption. The effect of water absorption on mechanical properties was more pronounced at high fiber content than at the low fiber content. Santulli [60] studied the post-impact behaviour of plain-woven jute/polyester composites subjected to low velocity impact and found that the impact performance of these composites was poor. Amash and Zugenmaier [61] reported on the effectiveness of cellulose fiber in improving the stiffness and reducing the damping in polypropylene-cellulose composites. A number of reports are available on investigations carried out on various aspects of polymer composites reinforced with banana fibers [62-65].

2.3 On Coir and Coir Fiber Reinforced Composites

Coconut coir fiber is the seed hair or husk. Husk of coconut is easily available in large quantities as residue from coconut production in many areas. Coir is a lingo-cellulosic natural fiber. The coir fiber industry is the one of the important industry of some areas of the developing world because of the advantages like hard-wearing quality, durability etc. These have wide application in of floor furnishing materials, yarn, rope etc. However, these coconut coir uses consume only a small percentage of the potential total world production of coconut husk. Hence, research and development efforts have been going on to find out the new areas for coir, along with utilization of coir as reinforcement in polymer composites. Verma et al.

[9] studied a detail review on the coir fiber reinforcement and application in polymer composites. Harish et al. [44] studied the mechanical behaviour such as tensile strength, flexural strength and impact strength of coir/epoxy composites. Ayrilmis et al. [66] studied on coir fiber reinforced polypropylene composite panel for automotive interior applications.

This study showed that the coir fiber is a potential candidate in the manufacture of reinforced thermoplastic composites, especially for partial replacement of high-cost and heavier glass fibers. Monteiro et al. [50] studied the mechanical performance of coir fiber/polyester composites. Mahzan et al. [67] studied the viability of coir fiber reinforced composites in sound absorption panel. Slate [68] investigated the mechanical properties of coir fiber

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reinforced cement sand mortar. Geethamma et al. [69] studied the dynamic and mechanical properties of short coir reinforced natural rubber composites. Li et al. [70] reported that flexural toughness and flexural toughness index of cementitious composites with coir fiber increased by more than 10 times. Misra et al. [71] investigated fire retardant coir epoxy micro-composites. Bujang et al. [72] studied the dynamic characteristics of coir fiber reinforced composites. Biswas et al. [73] studied the effect of coir length on mechanical behaviour of coir fiber reinforced epoxy composites. It has been reported that the hardness is decreasing with the increase in fiber length up to 20 mm. Romli et al. [74] done a study on the tensile properties of coir fiber reinforced epoxy composites. In their study, the volume fraction, curing time and compression load during the solidification of composites were taken as parameters. From the results, they concluded that volume fraction significantly influences the tensile strength of the composites. Junior et al. [75] studied the tensile behaviour of coir fiber reinforced polyester composites. Coir fiber polyester composites were tested as helmets, as roofing and post-boxes [76]. Development of composite materials for buildings using coconut coir with low thermal conductivity is an interesting alternative which would solve environment and energy concern [77, 78]. These composites, with coir loading ranging from 9 to 15 wt%, have a flexural strength of about 38 MPa. Coir has also been tested as filler or reinforcement in different composite materials [79-82]. Due to lowest thermal conductivity and bulk density coconut coir gives the most interesting products. The addition of coconut coir reduced the thermal conductivity of the composite specimens and produced a lightweight product. Coir polyester composites with untreated and treated coir fibers were studied for various mechanical properties [83].

2.4 Use of Fillers in Polymer Composites

Generally, fillers are used in polymers for a variety of reasons such as cost reduction, improved processing, density control, optical effects, thermal conductivity, control of thermal expansion, electrical properties, magnetic properties, flame retardancy, improved hardness and wear resistance. Now-a-days, particulate fillers consisting of ceramic or metal particles are being used to improve the performance of polymer composites to a great extent [84]. It is reported that the effect of these fillers has significant influence on the various properties of composites. A great deal of work has been done on the use of different types of fillers in improving the performance of polymer composites. Various kinds of polymers and polymer matrix composites reinforced with metal particles have a wide range of industrial applications such as heaters, electrodes [85], composites with thermal durability at high temperature etc. [86]. Similarly, ceramic filled polymer composites have also been the

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subject of extensive research in last two decades. When silica particles are added into a polymer matrix, they play an important role in improving electrical, mechanical and thermal properties of the composites [87, 88]. The mechanical properties of particulate filled polymer composites depend strongly on the particle size, particle-matrix interface adhesion and particle loading. Sumita et al. [89] underlined the interest of replacing micro-scale silica by its nano-scale counterpart, since nano-scale silica particles possess superior mechanical properties. Smaller particle size yields higher fracture toughness also for calcium carbonate filled high density polyethylene [90]. Similarly, epoxy filled with smaller alumina trihydrate particles shows higher fracture toughness [91]. Thus, particle size is being reduced rapidly and many recent studies have focused on how single-particle size affects mechanical properties [92-98]. Yamamoto et al. [99] reported that the structure and shape of silica particle have significant effects on the mechanical properties such as fatigue resistance, tensile and fracture properties. Nakamura et al. [100-102] discussed the effects of size and shape of silica particle on the strength and fracture toughness based on particle-matrix adhesion and also found an increase in the flexural and tensile strength as specific surface area of particles increased. Usually, the strength of a composite strongly depends on the stress transfer between the particles and the matrix [103]. For well-bonded particles, the applied stress can be effectively transferred to the particles from the matrix resulting in an improvement in the strength. However, for poorly bonded micro-particles, reduction in strength is found to have occurred. Nicolais and Nicodemo [104] studied the effect of particle shape on tensile properties of glassy thermoplastic composites. While most of these investigations have focused either on the particle shape or on particle size, the study made by Patnaik et al. [105] reported that the mechanical properties of polyester based hybrid composites are highly influenced also by the type and content of the filler materials.

2.5 On Erosion of Polymer Composites

Solid particle erosion, a typical erosive wear mode, is the loss of material that results from repeated impact of small, solid particles. When the angle of impingement is small, the wear produced is closely analogous to abrasion. When the angle of impingement is normal to the surface, material is displaced by plastic flow or is dislodged by brittle failure. Now-a-days polymers and related composites are extensively used as structural materials in various components and engineering systems where they encounter solid particle erosion. The variables affecting the severity of erosion can be interactive and include particle size, mass, shape and velocity together with the flux of erosive particles and their angle of impact. Many investigations have been done on the solid particle erosion behaviour of

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polymer and polymer based composites. Polymers that have been reported in the literature include polystyrene [106], polypropylene [107, 108], nylon [109], polyethylene [110], ultra- high molecular weight polyethylene [111], polyetheretherketone [112], polycarbonate and polymethylmethacrylate [113], epoxy [114], bismileimide [115], elastomers [116, 117] and rubber [118]. Barkoula and Karger-Kocsis [119] have also presented a detailed review on important variables in erosion process and their effects on different classes of polymers and their composites. Tilly and Sage [114] tested nylon and epoxy reinforced with carbon, glass, or steel. Further, Miyazaki and Hamao [120] carried out another similar study on the erosion behaviour of short fiber reinforced thermoplastic resins with special attention focused on an incubation period of erosion. Pool et al. [16] used sand particles to erode a unidirectional continuous graphite fiber reinforced polyimide laminate, a woven graphite-fiber-reinforced epoxy laminate, a woven Aramid-fiber-reinforced epoxy laminate and a chopped-graphite- fiber reinforced poly(phenylene sulfide). Tilly [121] investigated the solid particle erosion behaviour of Nylon 66 and graphite-fiber-reinforced Nylon 66 by impingement of quartz particles. Harsha et al. [122] reported the influence of impingement angles and impact velocities on solid particle erosion of various polyaryletherketones and their composites with short fiber reinforcement. In another study, Arjula and Harsha [123] have discussed the usefulness of the erosion efficiency parameter to identify various mechanisms in solid particle erosion. This study presents extensively on the erosion response, erosion efficiency and wear mechanisms of various polymers and composites. Zahavi and Schmitt [124]

investigated the erosive behaviour of sand on quartz-polyimide, glass cloth-epoxy and quartz-polybutadiene composites. Recently, few studied has been made on solid particle erosion behaviour of glass fiber reinforced polyester composites [125-129]. Miyazaki and Hamao [130] studied the effect of matrix materials, reinforcement fibers, fiber-matrix interface strength, impact angle and particle velocity on the solid particle erosion behaviour of fiber reinforced plastics. They observed that the erosion rate of a FRP decreases with the increase in the interface strength between matrix material and fibers. A study by Tewari et al [131], on the influence of impingement angles and fiber orientations concludes that unidirectional carbon and glass fiber reinforced epoxy composites show semi ductile erosion behaviour, with the maximum erosion rate occurring at 60° impingement angle. In another investigation, Barkoula and Karger-Kocsis [132] studied the effects of fiber content and relative fiber orientation on the solid particle erosion of glass fiber/polypropylene composites. It is evident from the available literature that the presence of particulate fillers has significant influence on various properties of polymer composites. But as far as the erosion behaviour of composites reinforced with both particulates and fibers is concerned, in

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fact, very limited work has been reported in the literature. As a result, there is no clear understanding of the mechanism of erosion in such polymer composites. Thus, a possibility that the incorporation of both particles and fibers in polymer could provide an improved wear performance has not been adequately explored so far. However, few recent publications by Patnaik et al. [126-128] on erosion wear characteristics of glass-polyester composites filled with different particulate fillers suggest that in such hybrid composites, the rate of material loss due to solid particle erosion reduce significantly with the addition of hard particulate fillers into the matrix. This improvement in the wear resistance depends on both the type and the content of filler.

2.6 On TOPSIS

TOPSIS is a MCDM approach to identify solutions from a finite set of alternatives based upon simultaneous minimization of distance from an ideal point and maximization of distance from a nadir point. TOPSIS has been applied to a number of applications by many researchers. Waigaonkar et al. [133] used TOPSIS method for resin selection in rotational molding. Sawant et al. [134] used PSI and TOPSIS method for automated guided vehicle selection. They proposed an automated guided vehicle selection index to evaluate and rank automated guided vehicle for the given application. Gadakh [135] used TOPSIS method for parametric optimization of wire electrical discharge machining. TOPSIS has been successfully applied to the areas of human resources management [136], transportation [137], product design [138], manufacturing [139], water management [140], quality control [141], and location analysis [142]. This includes a computer-aided evaluation and optimal selection procedure for robot and robot grippers [143, 144], optimal selection of motor vehicles [145], optimal selection of materials for engineering applications [146], and optimal selection of composite product system [147]. A combined TOPSIS-AHP method is used for non- traditional machining processes selection by Chakladar and Chakraborty [148]. The use of TOPSIS method to assess the mobile phone options in respect to the user‘s preferences order is done by Isiklar and Buyukozkan [149]. A study on customer-driven product design using AHP and TOPSIS method is done by Lin et al. [150]. A combined DEA and TOPSIS method for solving flexible bay structure layout is done by Ghaseminejad et al. [151]. It is found that this method is useful for creating, initial layout, generating initial layout alternatives and evaluating them. A MCDM approach based on ANP-TOPSIS is used to evaluate suppliers in Iran‘s auto industry by Shahroudi and Rouydel [152]. The selection of an optimal refinement condition to achieve maximum tensile properties of Al-15%Mg2Si composite based on TOPSIS method is done by Khorshid et al. [153]. It is observed that the TOPSIS method is

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considered to be a suitable approach in solving material selection problem. Singh et al. [154]

studied the selection of material for bicycle chain in Indian scenario using MADM Approach.

They concluded that both MADM and TOPSIS methods user friendly for the ranking of the parameters. Huang et al. [155] studied the MCDM and uncertainty analysis for materials selection in environmentally conscious design.

2.7 The Knowledge Gap in Earlier Investigations

The literature survey presented above reveals the following knowledge gap in the research reported so far:

o Though much work has been done on a wide variety of natural fibers for polymer composites, very less has been reported on the reinforcing potential of coir fiber in spite of its several advantages over others. Many low-end application areas are cited in the literature for coir based products, but there is hardly any mention of their potential use in tribological situations where synthetic fibers are widely used.

Moreover, there is no report available in the literature on the erosion characteristics of coir based polymer composites.

o A number of research efforts have been devoted to the mechanical and wear characteristics of either fiber reinforced composites or particulate filled composites.

However, a possibility that the incorporation of both particulates and fibers in polymer could provide a synergism in terms of improved performance has not been adequately addressed so far.

o TOPSIS method is an efficient tool for solving many MCDM problems. However, it is hardly been used for selection of composite materials based on their mechanical and erosion wear properties.

2.8 Objectives of the Present Work

The knowledge gap in the existing literature summarized above has helped to set the objectives of this research work which are outlined as follows:

1. Fabrication of a series of coir fiber reinforced epoxy composites with varying the weight percentage of fiber and fiber length.

2. To study the physical, mechanical and wear behaviour such as density, water absorption, tensile strength, tensile modulus, flexural strength, impact strength, hardness, erosion wear rate of the composites

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3. To study the effect of fiber content, fiber length and Al2O3 filler on the physical, mechanical, water absorption and erosion wear behaviour of the composites.

4. To study the effect of impingement angle and impact velocity on the erosion wear behaviour of the composites.

5. Comparison of properties of the coir fiber reinforced epoxy composites without filler and Al2O3 filled coir fiber reinforced epoxy composites

6. To study the surface morphology of the eroded composite specimens in order to identify the possible wear mechanisms using SEM.

7. Ranking of composites using TOPSIS method on the basis of their physical, mechanical, water absorption and erosion wear properties.

Chapter Summary This chapter has provided

 An exhaustive review of research works on various aspects of polymer composites reported by previous investigators

 The knowledge gap in earlier investigations

 The objectives of the present work

The next chapter describes the materials and methods used for the processing of the composites, the experimental planning and the TOPSIS method.

********

References

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